| Method and apparatus for providing a rate control for interlace coding -> Monitor Keywords |
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Method and apparatus for providing a rate control for interlace codingRelated Patent Categories: Pulse Or Digital Communications, Bandwidth Reduction Or Expansion, Television Or Motion Video Signal, PredictiveMethod and apparatus for providing a rate control for interlace coding description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060209954, Method and apparatus for providing a rate control for interlace coding. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] Embodiments of the present invention generally relate to an encoding system. More specifically, the present invention relates to a rate control method that is employed in a motion compensated encoder. [0003] 2. Description of the Related Art [0004] Demands for lower bit-rates and higher video quality requires efficient use of bandwidth. To achieve these goals, the Moving Picture Experts Group (MPEG) created the ISO/IEC international Standards 11172 (1991) (generally referred to as MPEG-1 format) and 13818 (1995) (generally referred to as MPEG-2 format), which are incorporated herein in their entirety by reference. Although these encoding standards were very effective, new and improved encoding standards, e.g., H.264/MPEG-4 AVC, have been developed. [0005] H.264/MPEG-4 AVC is a new video coding standard that achieves data compression by utilizing the coding tools, such as spatial and temporal prediction, transform and quantization, entropy coding, and etc. Unlike other existing video coding standards, H.264 supports frame coding, field coding and picture adaptive frame and field coding. Hence, the rate control methods designed based upon other existing video coding standards, for example, the MPEG-2 TM5 rate control, may not readily be applicable to H.264 encoder directly. [0006] Thus, there is a need in the art for a rate control method that can be deployed in new encoding standards such as H.264/MPEG-4 AVC. SUMMARY OF THE INVENTION [0007] In one embodiment, the present invention discloses a system and method for providing a rate control to an encoder, e.g., a H.264/MPEG-4 AVC compliant encoder. For example, the rate control method computes a target group of pictures (GOP) rate for a GOP of the input image sequence. The rate control method then computes a target rate per picture from the target GOP rate. In one embodiment, the target rate comprises at least one of: a frame picture target rate and a field picture target rate, wherein the field picture target rate is computed in accordance with two complexity measures for two predicted (P) fields, one complexity measure for one intra (I) field and one complexity measure for one bi-predicted (B) field. [0008] In an alternative embodiment, a novel rate control method computes a buffer fullness and then adjusts the buffer fullness in accordance with a total activity measure or a total cost measure. The adjusted buffer fullness is then used to compute a quantization stepsize and/or a quantization parameter. Finally, each macroblock can be encoded in accordance with said quantization parameter (QP). [0009] In one embodiment, the quantization parameter is optionally adaptively adjusted in accordance with spatial local activity. BRIEF DESCRIPTION OF THE DRAWINGS [0010] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0011] FIG. 1 illustrates a motion compensated encoder of the present invention; [0012] FIG. 2 illustrates a method for performing rate control of the present invention; and [0013] FIG. 3 illustrates the present invention implemented using a general purpose computer. [0014] To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0015] It should be noted that although the present invention is described within the context of H.264/MPEG-4 AVC, the present invention is not so limited. Namely, the present motion compensated encoder can be an H.264/MPEG-4 AVC compliant encoder or an encoder that is compliant to any other compression standards that are capable of exploiting the present rate control scheme. [0016] FIG. 1 depicts a block diagram of an exemplary motion compensated encoder 100 of the present invention. In one embodiment of the present invention, the apparatus 100 is an encoder or a portion of a more complex motion compensation coding system. The apparatus 100 comprises a temporal or spatial prediction module 140 (e.g., comprising a variable block motion estimation module and a motion compensation module), a rate control module 130, a transform module 160, e.g., a discrete cosine transform (DCT) based module, a quantization (Q) module 170, a context adaptive variable length coding (CAVLC) module or context-adaptive binary arithmetic coding module (CABAC)180, a buffer (BUF) 190, an inverse quantization (Q.sup.-1) module 175, an inverse DCT (DCT.sup.-1)transform module 165, a subtractor 115, a summer 155, a deblocking module 151, and a reference buffer 150. Although the apparatus 100 comprises a plurality of modules, those skilled in the art will realize that the functions performed by the various modules are not required to be isolated into separate modules as shown in FIG. 1. For example, the set of modules comprising the temporal or spatial prediction module 140, inverse quantization module 175 and inverse DCT module 165 is generally known as an "embedded decoder". [0017] FIG. 1 illustrates an input video image (image sequence) on path 110 which is digitized and represented as a luminance and two color difference signals (Y, C.sub.r, C.sub.b) in accordance with the MPEG standards. These signals can be further divided into a plurality of layers (sequence, group of pictures, picture, slice and blocks) such that each picture (frame) is represented by a plurality of blocks having different sizes. The division of a picture into block units improves the ability to discern changes between two successive pictures and improves image compression through the elimination of low amplitude transformed coefficients. The digitized signal may optionally undergo preprocessing such as format conversion for selecting an appropriate window, resolution and input format. [0018] The input video image on path 110 is received into temporal or spatial prediction module 140 for performing spatial prediction and for estimating motion vectors for temporal prediction. In one embodiment, the temporal or spatial prediction module 140 comprises a variable block motion estimation module and a motion compensation module. The motion vectors from the variable block motion estimation module are received by the motion compensation module for improving the efficiency of the prediction of sample values. Motion compensation involves a prediction that uses motion vectors to provide offsets into the past and/or future reference frames containing previously decoded sample values that are used to form the prediction error. Namely, the temporal or spatial prediction module 140 uses the previously decoded frame and the motion vectors to construct an estimate of the current frame. [0019] The temporal or spatial prediction module 140 may also perform spatial prediction processing, e.g., directional spatial prediction (DSP). Directional spatial prediction can be implemented for intra coding, for extrapolating the edges of the previously-decoded parts of the current picture and applying it in regions of pictures that are intra coded. This improves the quality of the prediction signal, and also allows prediction from neighboring areas that were not coded using intra coding. [0020] Furthermore, prior to performing motion compensation prediction for a given block, a coding mode must be selected. In the area of coding mode decision, MPEG provides a plurality of different coding modes. Generally, these coding modes are grouped into two broad classifications, inter mode coding and intra mode coding. Intra mode coding involves the coding of a block or picture that uses information only from that block or picture. Conversely, inter mode coding involves the coding of a block or picture that uses information both from itself and from blocks and pictures occurring at different times. Continue reading about Method and apparatus for providing a rate control for interlace coding... Full patent description for Method and apparatus for providing a rate control for interlace coding Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for providing a rate control for interlace coding patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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